JPH10152372A - Barium titanate-based semiconductor porcelain and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce a semiconductor porcelain, capable of suppressing a rise in resistance value, improving the breakdown voltage and manifesting a positive resistance temperature coefficient by forming a composition containing a system, prepared by adding Bi2 O3 to barium titanate containing Y as a compositional system for providing a small average grain diameter within a specific range and mixed with a system obtained by adding Li2 CO3 to the barium titanate containing the Y as a compositional system for affording a large average grain diameter within a specified range. SOLUTION: This barium titanate-based semiconductor porcelain comprises large crystal grains having 20-30μm average grain diameter and small crystal grains having 1.0-5.0μm average diameter. When the average grain diameter of the large grain crystals is larger than 30μm, the mutual contact of the grains is increased to cause a deterioration in breakdown voltage and resistance value. When the average grain diameter of the small crystal grains is smaller than 1.0μm, a definite granular form is not manifested and the resistance value is raised to provide an insulator. At least either one of the two compositional systems is calcined and both are then mixed to carry out the glost firing. Thereby, a sintered compact having the large and the small grain diameters is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a barium titanate-based semiconductor porcelain whose resistance value sharply increases at a specific temperature and a method of manufacturing the same.

[0002]

2. Description of the Related Art Barium titanate is converted into a semiconductor by adding a small amount of a rare earth element, and has a positive resistance temperature coefficient (Positive Temperature Coefficient: P) near its Curie point.
(TC characteristic) has been widely known. Utilizing the PTC characteristics, it has been applied to various uses such as an overcurrent protection element, a temperature control element, a motor starting element, and a heater.

It is desirable that the crystal grains of the sintered body of the barium titanate-based semiconductor porcelain be uniform in view of its characteristics. However, in general, general crystal grains are often inhomogeneous, We are developing and improving uniform crystal grains from the process aspect.

[0004]

However, as the crystal grain size increases, the temperature coefficient of resistance tends to deteriorate, and the breakdown voltage tends to decrease. On the other hand, when the crystal grain size decreases, the resistance increases and the insulator tends to be formed. There is. Therefore, it has been difficult to suppress an increase in the resistance value and improve the breakdown voltage.

[0005] In order to solve the above-mentioned problems, the present invention provides crystal grains having a large average particle diameter (for example, 20 to 30 µm).
An object of the present invention is to improve the characteristics of barium titanate-based semiconductor ceramics exhibiting a positive temperature coefficient of resistance by forming two different crystal particle diameters of small crystal particles (for example, 1.0 to 5.0 μm). It is.

[0006]

In order to solve the above problems SUMMARY OF THE INVENTION The invention of Claim 1 of the present invention, a composition system to provide a small average particle diameter, Bi ₂ barium titanate containing Y as a semiconductive dopant A composition in which a system obtained by adding O ₃ and a system obtained by adding Li ₂ CO ₃ to barium titanate containing Y as a semiconductor element as a composition system giving a large average particle size is formed. Thus, a barium titanate-based semiconductor porcelain can be obtained which suppresses a rise in resistance value and improves a breakdown voltage.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION The invention according to claim 1 of the present invention provides a composition system which gives a small average particle size, a system obtained by adding Bi ₂ O ₃ to barium titanate containing Y as a semiconducting element, As a composition system giving a large average particle diameter, a composition in which a system obtained by adding Li ₂ CO ₃ to barium titanate containing Y as a semiconducting element is formed to form a mixed composition, and the resistance value increases. It is possible to obtain a barium titanate-based semiconductor porcelain which suppresses and improves the breakdown voltage.

The average particle size of the large crystal particles is 20
The average particle size of the small crystal particles is 1.0 to 30 μm.
5.0 μm is desirable for improving the characteristics. The reason is as follows. (1) When the average particle diameter of the large crystal particle diameter is larger than 30 μm, the contact between the large particles increases, and the breakdown voltage and the resistance value decrease. (2) When the average particle diameter of the small crystal particle diameter is smaller than 1.0 μm, the particles do not show a clear particle morphology, and accordingly, the resistance value increases and the tendency to form an insulator is recognized.

Further, in the manufacturing method of the present invention, Bi ₂ O ₃ is added to barium titanate containing Y as a semiconducting element, and Li ₂ CO ₃ is added to barium titanate containing Y as a semiconducting element. At least one of the added materials is calcined, then mixed and subjected to main firing, so that a sintered body having two different particle sizes, large and small, can be obtained. An improvement in voltage is achieved.

[0010]

Embodiments of the present invention will be described below.

Example 1 Barium carbonate (BaCO)_Three)
 1.0 mol, titanium oxide (TiO_Two) 1.01m
ol, yttria (Y_TwoO_Three) 0.0024 mol, 2
Silicon oxide (SiO _Two) 0.024 mol, man nitrate
Gun (Mn (NO_Three)_Two) 0.0003mol, Bi oxide
Smas (Bi_TwoO_Three) 0.0003-0.001mol
Are weighed and wet-mixed by a ball mill for 20 hours. Next
These are dried and temporarily molded, and then dried at 1100 ° C in air for 2 hours.
Calcination for a period of time (hereinafter referred to as Bi-calcination powder).

On the other hand, 1.0 mol of BaCO ₃ and TiO _{2
1.01mol, Y 2 O 3 0.0024mol,} Si
O ₂ 0.024 mol, Mn (NO ₃ ) ₂ 0.000
3 mol, Li ₂ CO ₃ 0.001 to 0.003 mol
Are weighed and mixed, dried and calcined in the same manner as Bi-calcined powder (hereinafter referred to as Li-calcined powder).

Next, the Bi-calcined powder obtained above and Li
-Simultaneous wet mixing of calcined powder by ball mill for 20 hours
After pulverizing, drying, granulating and molding. Further, this compact is fired in the atmosphere at 1350 ° C. for 1 hour to obtain a barium titanate-based semiconductor porcelain. After this sintered body was subjected to nickel plating, a silver paste was baked at 550 ° C. for 10 minutes to form an electrode.

The compositions of the barium titanate-based semiconductor ceramic thus obtained are shown in Tables 1 to 8 below.
The results of measuring the specific resistance (ρ ₂₅ ), the breakdown voltage, and the temperature coefficient of resistance (α) are shown in Tables 1 to 8. In Table 1 below, BaCO ₃ , TiO ₂ , Y ₂ O ₃ , SiO ₂ , Mn
The composition containing (NO ₃ ) ₂ was defined as the basic composition, and the system was prepared by adding Bi to the basic composition, and the system was prepared by adding Li to the system 2.

[0015]

[Table 1]

[0016]

[Table 2]

Example 2 1.0 mol of BaCO ₃ ,
TiO ₂ 1.01mol, Y ₂ O ₃ 0.0024mo
1, 0.024 mol of SiO ₂ , Mn (NO ₃ ) ₂
0.0003mol, Li ₂ CO ₃ 0.001~0.0
03 mol is weighed, and the Bi-calcined powder obtained in (Example 1) is further added thereto, and wet-mixed by a ball mill for 20 hours. A sample is prepared in the same manner as described below (Example 1). With respect to the barium titanate-based semiconductor porcelain thus obtained, the composition was set to the sample numbers 9 to 16 in (Table 1),
What measured the characteristic was shown to the sample numbers 9-16 of (Table 2).

Comparative Example 1 As a comparative example, the additive amount of Bi ₂ O ₃ in the above embodiment was 0.0003 mol or less and 0.1%.
001 mol or more, and the added amount of Li ₂ CO ₃ is 0.00
Samples of 1 mol or less and 0.003 mol or more were prepared in the same manner as in (Example 1), and the characteristics were evaluated. The composition was shown in Sample Nos. 17 to 20 of (Table 1), and the characteristic values were shown in Sample Nos. 17 to 20 of (Table 2).

(Comparative Example 2) Sample Nos. 21 and 2 in (Table 1)
Bi ₂ O ₃ and Li ₂ CO ₃ were added from the beginning to the basic composition so that the composition became 4.
Wet mix for hours. Subsequent sample preparation steps are the same as in (Example 1). The characteristics of the device thus obtained were measured, and the results are shown in Sample Nos. 21 to 24 of (Table 2).

Hereinafter, the present invention will be described with reference to the above Examples and Comparative Examples. (1) According to Example 1 (Sample Nos. 1 to 8) and Comparative Example 1 (Sample Nos. 17 to 20), the added amounts of Bi ₂ O ₃ and Li ₂ CO ₃ were 0.0003 to 0.001 mol, respectively. 00
When the amount is outside the range of 1 to 0.003 mol, there is no difference in particle diameter, the specific resistance increases, the breakdown voltage is as low as about 150 V, and no improvement in characteristics is observed. (2) Example 1 and Example 2 (Sample Nos. 1 to 16) and Comparative Example 2 (Sample Nos. 21 to 24, composition system 1 containing Bi ₂ O ₃ (Table 1) and Li ₂ CO ₃ were used. Composition system (Table 1)
After each of the composition systems 2 is separately mixed, at least one of them is calcined to have a larger average particle diameter (20 to 30).
μm) and a smaller one (1.0 to 5.0 μm) can be formed, thereby improving the characteristics. In addition, in Examples 2 of Sample Nos. 9 to 16 in (Table 1), similarly, in the case where the composition system 1 was not calcined and the composition system 2 was calcined, the improvement of the characteristics was similarly observed. Li ₂ CO ₃ and lithium oxide Li ₂
Even when O was used, the same effect as the present invention was obtained.

As described above, a composition obtained by adding 0.0003 to 0.001 mol of Bi ₂ O ₃ to barium titanate containing Y as a semiconducting element, and a composition obtained by adding barium titanate containing Y as a semiconducting element, 0.001-0.003m
ol of the composition obtained by adding Li, and separately mixing and calcining at least one, and then simultaneously mixing both,
In the case of final sintering, particles having a large average particle diameter (20 to
30 μm) and small particles (1.0 to 5.0 μm) were formed, thereby suppressing an increase in resistance value. A barium titanate-based semiconductor porcelain having a high breakdown voltage can be obtained.

[0022]

As described above, according to the present invention, in the barium titanate-based semiconductor ceramic material, crystal grains having a large average particle diameter (20 to 30 μm) and small crystal grains (1.
By forming a sintered body having two different crystal grains (0 to 5.0 μm), an increase in resistance is suppressed,
Further, a barium titanate-based semiconductor ceramic exhibiting a positive temperature coefficient of resistance with improved breakdown voltage can be obtained.

Claims (2)

[Claims] 1. A barium titanate-based semiconductor having an average particle diameter of 1.0 to 5.0 μm obtained by adding 0.0003 to 0.001 mol of Bi ₂ O ₃ to barium titanate containing Y as a semiconductor element. Crystal grains made of a porcelain material and barium titanate containing Y as a semiconducting element
Li ₂ CO ₃ added to the crystal grains having an average particle size of from barium titanate-based semiconductor ceramic material 20~30μm comprising the barium titanate-based semiconductor ceramic mix of ～0.003Mol. 2. A composition comprising 0.0003 to 0.001 mol of Bi ₂ O ₃ added to barium titanate containing Y as a semiconducting element, and 0.1% to 0.2 wt% of barium titanate containing Y as a semiconducting element. 001 to 0.003 mol of Li
_{2 A} method for producing a barium titanate-based semiconductor porcelain, in which at least one of the compositions to which CO ₃ is added is calcined, then the two are mixed and finally sintered.